‰  NOW 35 WPM  ‰  TEXT IS FROM OCTOBER 2018 QST  PAGE 42‰

IN THE CASE OF FSK TRANSMISSIONS, IT WILL BE NECESSARY TO GIVE THE PTT
DRIVER SOME HANG TIME.  THATS THE FUNCTION OF THE RE TRIGGERABLE TIMER U3B
AND ASSOCIATED COMPONENTS.  SW4 ALLOWS THE USER TO SELECT WHETHER THE PTT
FOLLOWS THE CONTROL TONE WITH OR WITHOUT PTT HANG TIME.  WHEN OPERATING IN
AFSK MODE, SWITCH SW4 IS SET TO THE OUTPUT OF Q1 U3A, WHICH WILL CAUSE THE
TRANSMITTER PTT TO VERY CLOSELY 4 MS FOLLOW THE TRANSMITTER CONTROL TONE.
THE CW RELAY IS ALWAYS DRIVEN BY Q1 WITH NO TX HANG TIME.  FOR FSK
OPERATION, THE CONTROL TONE NOT ONLY REPRESENTS THE MARK ONE FOR THE FSK
CONTROL INPUT TO THE TRANSMITTER, THAT SAME TONE WILL BE USED TO CONTROL
THE TRANSMITTER PTT.  IN THIS CASE, WE NEED SOME TRANSMITTER HANG TIME TO
BRIDGE THE TIMES WHEN FSK SPACE IS BEING TRANSMITTED.  SO FOR FSK
TRANSMISSION, SW4 IS SET TO THE OUTPUT OF Q3.  YOU DONT NECESSARILY NEED TO
USE RELAYS BECAUSE YOU COULD USE ONE OR TWO TRANSISTORS TO PROVIDE AN OPEN
COLLECTOR OR OPEN DRAIN OUTPUT TO CONTROL THE TRANSMITTER PTT AND CW
CIRCUITS.  I USED A PAN CHANG SIP 1A05 REED RELAY.  IT TAKES NO MORE THAN
300 US TO ACTIVATE OR RELEASE, EVEN WITH THE INCLUDED VOLTAGE SNUBBER DIODE
ACROSS THE COIL.  THE CONTACT BOUNCE TIME DURING ACTIVATION IS INCLUDED IN
THAT 300 US.  CAUTION SNUBBER CIRCUITS, LIKE THE REVERSE BIASED DIODE ON
RELAY COILS, CAN SIGNIFICANTLY DELAY THE RELEASE TIME OF A RELAY WHEN THE
‰  END OF 35 WPM TEXT  ‰  QST DE W1AW  ƒ